The conventional flashlight employs a paraboloidal reflector to direct the light emitted from the lamp to the scene to be illuminated. For simplicity of explanation, consider the light source to be a point. If the point light source is positioned at the focus of the paraboloid, a concentrated beam is formed. This beam is the size of the maximum diameter of the reflector and is referred to as the spot beam. Some flashlights have a means to position the lamp to a different location along the axis of the reflector either by moving the lamp or the reflector. These flashlights are referred to as adjustable or focusable flashlights. When the point source of light is displaced from the focal point along the axis of the reflector, the beam that is formed illuminates a larger area of the scene. As the light source is displaced farther from the focal point, the beam gets larger and an unilluminated center disc is formed. This beam is referred to as the broad beam and the unilluminated disc is referred to as the black spot.
The Ellion reflector of U.S. Pat. No. 4,984,140 is a modified paraboloid that eliminates the black spot in the broad beam.
The lamp is inserted into the reflector in the typical flashlight through a hole at the apex of the reflector. The portion of the reflector that accomodates the lamp is not a reflective surface and as a result will not reflect the emitted light. The hole through which the lamp is inserted in approximately 0.6 inch in diameter for the "D" size flashlight whose maximum diameter of the reflector is approximately 2 inches. The cross-sectional area of the hole is approximately nine percent of the area at the maximum diameter of the reflector. The other size flashlights have correspondingly sized holes and maximum diameters of the reflectors. As a result of the hole, approximately nine percent of the potential projected light is lost. In addition to this decrease in the amount of light that is reflected, there would be an unilluminated center disc for the spot beam that is formed from the ideal point light source.
It is the object of this invention to produce either a spot beam or a broad beam without the black spot with the use of a standard paraboloidal reflector. It is an additional objective of this invention to produce a brighter spot and broad beam by utilizing the area of the reflector near the apex of the reflector. It is another object of this invention to produce either a spot beam or a broad beam without requiring the movement of the lamp relative to the paraboidal reflector in the two filament embodiment. It is a further object of this invention to produce a spot beam or a broad beam without a black spot in the second embodiment using a conventional single filament lamp and a paraboloidal reflector by rotating the filament from a position that is perpendicular to the reflector axis to one that is in line with the reflector axis.